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George Jones

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Everything posted by George Jones

  1. At what were you looking, the Moon, or a star or a planet? What is the eye relief of the lens?
  2. Just in from seeing m57 with (15x70) bins for the first time. I saw M57 (not as a ring) as the bottom left of a bow tie made up of M57 and four stars. After etching this configuration in my mind, I came in a and took a look on Stellarium for confirmation. Observation made form the middle of a small (60,000) city.
  3. Yes, these are two different, but similar, things. One main difference is that one source of attraction, The Great Attractor, lies within our observable universe, while the source of attraction causing the dark flow seems to lie outside our observable universe. Still haven't run through this. It will take only a few quiet minutes, but my weekends are dominated by family time and non-quiet minutes.
  4. I first read (a couple of weeks ago) the 5" figure for contrast in The Backyard Astronomer's Guide by Dickenson and Dyer, but without any details. Last night, I decided to Google aorund a bit, which led me to Thierry Legault's very informative pages, Astrophotography - Thierry Legault. Click on "The obstrusction" in the menu at the bottom left. "Collimation" in the same menu is also very interesting, and somewhat surprising, at least for me. I have Legault's beautiful New Atlas of the Moon. Yes, beautiful report! I had hoped to view this through a new, small scope, but it seems that I'm getting jerked around by the shop from which I ordered the scope. If I get time, I'll start a thread on this.
  5. Talitha, I think I know from where the 5" comes, but it's not magnitude, it's contrast. An 8'' SCT with a 30% central obstruction has the same surface catching area, and thus the same image brightness, as a 7.5 or 7.6" refractor, as Warthog has noted. An 8'' SCT with a 30% central obstruction has the same image contrast as a 5 or 6'' refractor. (The central obstruction causes a change in the Airy diffraction pattern; the relative difference between the brightness of the disk and the first ring decreases as obstruction size increases.) An 8'' SCT with a 30% central obstruction has the same image resolution as an 8" refractor. (Since the obstruction is central, the maximum separation of useful light is stll 8".)
  6. Inflation lasted for the mind-booglingly short period of about 10-34 seconds during which time the scale of the universe grew by a mind-boggling factor of about 1050. Both of these numbers could be off by a few orders of magnitude. Sorry, I'm not sure what you mean. Actually, due to dark energy, the universe has now entered another period of exponential growth. The current exponential growth, however, is a lot more gradual than the inflationary growth. Something like this is thought to happen during and at the end of the universe's inflationary period. Inflation was caused by a field, and, during its inflationary period, this field lost potential energy as the universe expanded and cooled. Inflation ended as energy in the field was converted into new matter at a temperature similar to the universe's temperature at the start of inflation. This is called the reheating phase of the universe (as opposed to nuking last night's leftover pizza). The matter that was created during reheating eventually formed all the matter in universe today. It seems that the rate at which the universe loses energy (density), sometimes decreases and sometimes increases, but Wife just called and said that Wife and Daughter are about to drop in on me, and I haven't had time to check this thoroughly.
  7. Hi! I, too, joined recently. Seems to be an amazing group of people. This is exactly how I feel.
  8. Nice find, Rosanella. I think that cosmology is the most exciting field in physics these days, with interconnections between subatomic physics and the universe at large, and with mountains of new data arriving all the time. The idea is that this dark flow has a physical cause, possibly a gravitational attraction to a region where matter is more dense. Before inflation, the matter that we see streaming (called it S) was gravitationally attracted to the dense mass (call it M). In order for M to affect S, M must be able to throw photons or gravitons and hit M, or throw cricket balls (matter) and hit M, i.e., M must be able to transmit information to S at or below the speed of light. Physicists speculate that this was relationship between M and S before inflation, and that the rapid, accelerated expansion of inflation broke this causal relationship, so that M is now outside the observable universe. In other words, inflation accelerated M to a place somewhere over the rainbow ... er, I mean somewhere over the cosmological horizon. An even more specific conclusion can be drawn: there is a happy hour special on pan-galactic gargle blasters at the Restaurant at the End of the Universe .
  9. Yes, good. Let's check this by eliminating p and P in Kepler's third law. I get 2*pi*r 2*pi*R (--------)^2 = (----------)^2 v V ------------ ------------ . r^3 R^3Does this make sense? If not, ask some more questions. If so, rearrange this so that v^2 and V^2 are on one side of the equation, and r and R are on the other side.
  10. I hope your hand is healing well Let's step back from gravitational radiation for a bit and break things down into bits. First, consider speeds in orbits. For concreteness, take orbit 1 to be the orbit of the ISS about the Earth, and orbit 2 to a hypothetical larger orbit of the ISS about the Earth at the Moon's distance. In which orbit, 1 or 2, does the ISS have the greater speed? The answer to this question can worked out using Newton's laws, or using Kepler's third law, which comes from Newton's laws. I think that I want to use Kepler. Let the period and radius of orbit 1 be p and r, and the period and radius of orbit 2 be P and and R. Kepler's second law gives p^2/r^3 = P^2/R^3. Now, the period of each orbit is the distance around the orbit divided by the speed of ISS in orbit, P = 2 pi R/V and p = 2 pi r/v. I have used poor notation in that it is difficult to distinguish between upper case and lower case letters. Everything to with the larger orbit is upper case; everything to with lsmaller orbit is lower case. What happens when the expressions for the period are put into the expression fro Kepler's third law? Can R > r be used to tell which of v and V is bigger?
  11. I'm not sure what you mean by "the slowing down." The energy of the gravitational radiation comes from orbital energy, so gravitational radiation that streams away from the system causes orbital energy to decrease. This causes orbital radius and period to decrease, and orbital speed to increase.
  12. Hi from New Brunswick, Canada! Google brought me here, and, since the UK is the same number of timezones from me as Canada's west coast, I decided to register. Congrats on the Ashes win. I have been a member of my local astronomy club for three years, I have observed (very non-systematically!) with binoculars for years, and I recently ordered, but have yet to receive, a Sky-Watcher 127 Maksutov-Cassegrain. George
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